The described aspects relate generally to wireless communication systems. More particularly, the described aspects relate to techniques for video telephony setup with preconditions.
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division—Code Division Multiple Access (TD-CDMA), and Time Division—Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks. Furthermore, UMTS supports multiple radio access bearer (multi-RAB) capability, which allows simultaneous network communication with a user equipment (UE) over two or more radio access bearers. Therefore, in an aspect, multi-RAB functionality in UMTS allows for a UE to concurrently transmit and receive packet-switched (PS) and circuit-switched (CS) data. Another example of such a network is the Long Term Evolution (LTE), the radio access network using OFDMA technology, defined as a part of Evolved Packet System (EPS), a fourth generation (4G) standard developed by 3GPP for wireless communication of high-speed data for mobile phones and data terminals. LTE supports scalable carrier bandwidths, from 1.4 MHz to 20 MHz and supports both frequency division duplexing (FDD) and time-division duplexing (TDD). EPS, purely IP based or a flat packet-switched system, consists of E-UTRA (Evolved UMTS Terrestrial Radio Access) and EPC (Evolved Packet Core). The E-UTRA includes UEs and E-UTRAN (Evolved UMTS Terrestrial Radio Access Network). The E-UTRAN is referred to as evolved NodeB (eNB). The EPC, including S-GW, P-GW, MME, HSS and etc. are designed to replace the GPRS Core Network, supports seamless handovers for both voice and data to cell towers with older network technology such as GSM, UMTS, CDMA2000, Wireless Local Area Network (like Wi-Fi) and etc.
In LTE, a packet-switched video telephony (PSVT) call may be established between multiple UEs. The UE that originates the PSVT call may be referred to as a mobile originated (MO) device and the UE that receives the PSVT call may be referred to as a mobile terminated (MT) device. To provide a certain Quality of Service (QoS), an audio stream and a video stream of the PSVT call may be transmitted and received over one or more dedicated EPS bearers. The respective dedicated EPS bearers may request network resources for the audio stream and the video stream.
To minimize the occurrences of the scenario where the user of the MT device, i.e., the callee, answers the PSVT call but the PSVT call fails to be established because the network resources are not available, the callee may not be alerted until the network resources for both the audio stream and the video stream are reserved on both ends of the MO device and the MT device. As referenced herein, a callee may refer to the user of the MT device and a caller may refer to the user of the MO device.
However, because audio stream and video stream may be communicated over different dedicated EPS bearers, it is likely that the audio dedicated EPS bearer may be established more quickly than the video dedicated EPS bearer. A time interval between readiness of the two bearer may also be unpredictable. Further, in a congested scenario, video resources may not be available and there may be no signaling to notify the device that the video resources are not available. As such, the device may have to wait until a QoS timer expires before establishing a PSVT call having only audio stream. Thus, the call set up time for the audio portion of a PSVT call is generally extended from the call set up time of a typical voice call due to the unavailability of the video resources. The audio is the essential component of a conversational service and should be established as quickly as possible for a PSVT call to meet the same or better user experience than a VoIP call.